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SubjectRe: [PATCH] drm/stm: ltdc: use crtc_mode_fixup to update adjusted_mode clock
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Hi Philippe,

On Thursday, 25 January 2018 18:01:01 EET Philippe Cornu wrote:
> There is a difference between the panel/bridge requested pixel clock
> value and the real one due to the hw platform clock preciseness (pll,
> dividers...). This patch updates the adjusted_mode clock value with
> the real hw clock value so then attached encoder & connector can use
> it for precise timing computations.
>
> Signed-off-by: Philippe Cornu <philippe.cornu@st.com>
> ---
> drivers/gpu/drm/stm/ltdc.c | 35 +++++++++++++++++++++++++----------
> 1 file changed, 25 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
> index b48589343ae1..90b3de516c91 100644
> --- a/drivers/gpu/drm/stm/ltdc.c
> +++ b/drivers/gpu/drm/stm/ltdc.c
> @@ -428,12 +428,35 @@ static void ltdc_crtc_atomic_disable(struct drm_crtc
> *crtc, reg_set(ldev->regs, LTDC_SRCR, SRCR_IMR);
> }
>
> +static bool ltdc_crtc_mode_fixup(struct drm_crtc *crtc,
> + const struct drm_display_mode *mode,
> + struct drm_display_mode *adjusted_mode)
> +{
> + struct ltdc_device *ldev = crtc_to_ltdc(crtc);
> + int rate = mode->clock * 1000;
> +
> + /*
> + * TODO clk_round_rate() does not work yet. When ready, it can
> + * be used instead of clk_set_rate() then clk_get_rate().
> + */

Why does it fail ? Is it due to the STM clock source implementation ? This
looks like a big hack, I'd rather see clk_round_rate() being fixed.

> + clk_disable(ldev->pixel_clk);
> + if (clk_set_rate(ldev->pixel_clk, rate) < 0) {
> + DRM_ERROR("Cannot set rate (%dHz) for pixel clk\n", rate);
> + return false;
> + }
> + clk_enable(ldev->pixel_clk);
> +
> + adjusted_mode->clock = clk_get_rate(ldev->pixel_clk) / 1000;
> +
> + return true;
> +}
> +
> static void ltdc_crtc_mode_set_nofb(struct drm_crtc *crtc)
> {
> struct ltdc_device *ldev = crtc_to_ltdc(crtc);
> struct drm_display_mode *mode = &crtc->state->adjusted_mode;
> struct videomode vm;
> - int rate = mode->clock * 1000;
> u32 hsync, vsync, accum_hbp, accum_vbp, accum_act_w, accum_act_h;
> u32 total_width, total_height;
> u32 val;
> @@ -456,15 +479,6 @@ static void ltdc_crtc_mode_set_nofb(struct drm_crtc
> *crtc) total_width = accum_act_w + vm.hfront_porch;
> total_height = accum_act_h + vm.vfront_porch;
>
> - clk_disable(ldev->pixel_clk);
> -
> - if (clk_set_rate(ldev->pixel_clk, rate) < 0) {
> - DRM_ERROR("Cannot set rate (%dHz) for pixel clk\n", rate);
> - return;
> - }
> -
> - clk_enable(ldev->pixel_clk);
> -
> /* Configures the HS, VS, DE and PC polarities. Default Active Low */
> val = 0;
>
> @@ -528,6 +542,7 @@ static void ltdc_crtc_atomic_flush(struct drm_crtc
> *crtc, }
>
> static const struct drm_crtc_helper_funcs ltdc_crtc_helper_funcs = {
> + .mode_fixup = ltdc_crtc_mode_fixup,
> .mode_set_nofb = ltdc_crtc_mode_set_nofb,
> .atomic_flush = ltdc_crtc_atomic_flush,
> .atomic_enable = ltdc_crtc_atomic_enable,

--
Regards,

Laurent Pinchart

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